P0304 Code- already change plugs what’s next? (1 Viewer)

[h2opl20]

Hi all-

Vehicle is at 205k and it’s been running perfectly fine. Up until last week. Started idling high and loss of HP. Ended up getting an error code of p0304. Guy at the auto store suggested first changing spark plugs and I did. Ran perfectly fine for two days and then today started idling rough again with the check engine light, vsc track and vsc off light on. Checked the code again and same error code but the rough idling seems to have subsided.

I’m going to change my coil packs next. Trying to do cheap options before heading down the money road.

Any suggestions if the coil packs don’t fix the iissue? Waiting on delivery for packs but want. Suggestions.

Thanks!

 

[JT4runner]

Lots of people having issues with this lately. I had this happen about a month ago. Since you have the plugs changed I would check your ignition coil on cylinder 4. I believe P0304 is for cylinder 4 misfire. That would be my next step. You don't have to change all the ignition coils out. Just the one for cylinder 4. It shouldn't take you more than 10 mins to swap it out. The best replacement is the Denso ignition coil on Amazon.

 

[h2opl20]

Lots of people having issues with this lately. I had this happen about a month ago. Since you have the plugs changed I would check your ignition coil on cylinder 4. I believe P0304 is for cylinder 4 misfire. That would be my next step. You don't have to change all the ignition coils out. Just the one for cylinder 4. It shouldn't take you more than 10 mins to swap it out. The best replacement is the Denso ignition coil on Amazon.

Thanks! I was debating to only change cylinder 4 but decided to do all of them. As I was changing the spark plugs I noticed how grimy and even cracked some of the ignition coils were. So just to be sure, I’m going to change all of them.

 

[civil offroad]

@h2opl20 I had this happen last month. The only difference was mine was the number 2. I went in to replace all 8. Reasoning behind this was because I didnt know alot about the trucks history, I seen a suspicious oily residue on the even side of the engine, I dont know what the conditions of the plugs were, and since my work requires redundancy, quality assurance, and due diligence. I decided to just replace all 8 plugs and all 8 coils. This way, I knew what the condition was. Be careful with retightening the bolts for the air box which mount to the even side cylinder head. I broke both bolts and now will be getting those professionally removed and replaced.

So, I discovered. 5 of the 8 coils were aftermarket no names. 3 of the coils had no gaskets. 3 of the plug wells have oil. So, I now can rest easy knowing my rig is running well.

 

[h2opl20]

@h2opl20 I had this happen last month. The only difference was mine was the number 2. I went in to replace all 8. Reasoning behind this was because I didnt know alot about the trucks history, I seen a suspicious oily residue on the even side of the engine, I dont know what the conditions of the plugs were, and since my work requires redundancy, quality assurance, and due diligence. I decided to just replace all 8 plugs and all 8 coils. This way, I knew what the condition was. Be careful with retightening the bolts for the air box which mount to the even side cylinder head. I broke both bolts and now will be getting those professionally removed and replaced.

So, I discovered. 5 of the 8 coils were aftermarket no names. 3 of the coils had no gaskets. 3 of the plug wells have oil. So, I now can rest easy knowing my rig is running well.

What did you do with the oil in the plug wells? How’d you drain it, if you did? I did notice a little bit of oil in one of the plugs. Don’t remember which but I’ll find out when I change the coils

 

[civil offroad]

What did you do with the oil in the plug wells? How’d you drain it, if you did?

Prior to removing the plug, I put in a rag and shoved my air nozzle in there. It got most of the oil out, its not 100%.

 

[h2opl20]

So good news, changed the coil packs and the issue is solved. Been three days running and everything seems good!